Red: Cannot drag face when display is scaled (Win10)

[endo64]

Transparent faces filled by a draw box cannot dragged if Windows 10 display scaled (display setting scale > 100%)

view [
    base loose with [color: none] draw [
        fill-pen   white
        box        10x10 82x82
    ]
]

If 82x82 changed to 81x81 then it can be dragged.

Expected behavior

Base face should be draggable by mouse.

Actual behavior

Face cannot be dragged.

Steps to reproduce the problem

On Windows 10
Right click on desktop, select Display Settings
Change Scale and Layout setting to 125%
Execute the above script and try to click & drag the face.

Red version and build date, operating system with version.

Red 0.6.3 Build date: 21-Dec-2017/23:39:43+03:00
Windows 10 (x64)

[endo64]

If the box is rounded then it works: box 10x10 82x82 1

[qtxie]

I can reproduce it on Win10, but no problems on Win7.

[endo64]

Can someone please test and confirm that this works now.
I tested on Red 0.6.4 for Windows built 11-Jan-2019/5:18:27+03:00 commit #5e37a10
@greggirwin Then we can close this issue.

[hiiamboris]

No, it's still buggy on W7 x64.
Red 0.6.4 for Windows built 11-Jan-2019/5:18:27+03:00 commit #5e37a10

This is 80x80, draggable, all ok:

But this is what I get from 82x82 and 125% scaling factor:

It's still draggable but I have to aim at the thin white line to do so. draw bug?

[endo64]

@hiiamboris Thanks for testing.
It is funny a year ago @qtxie said I can reproduce it on Win10, but no problems on Win7. now it is the opposite :)

[greggirwin]

If developing software was easy, everyone would do it.

[hiiamboris]

It's an MS GDI+ bug. The one we know already (it craps with alpha=0). We just didn't know it also happens in this scenario.

When scaling is set to 125%, the bug seems to appear when:

• both box corners are at coordinates (4N+2), which makes them appear at half a pixel. Whatever happens there internally in GDI+, it makes the box transparent. (Just a thought: maybe they have some float-to-byte casting, where the alpha value transcends from high 255.99999s into 256.00000001 something, and becomes 0)
• box color should be fully opaque (alpha = 0)

Anyway. We can only work around this as long as we're using GDI+.

To test:

repeat x 10 [view compose/deep [box 200x200 loose draw [fill-pen white box 10x10 (161 + x * 1x1) ]]]

Every 4th box drawn is transparent